1. Field of the invention
The present invention relates to a pedestrian detection device that detects a collision between a vehicle and a pedestrian, an air bag associated with the pedestrian detection device, and a vehicle equipped with the air bag system.
2. Description of the Related Art
In the related art, a pedestrian detection device, adapted for installation on a vehicle to detect a collision between the vehicle and a pedestrian, has been proposed as disclosed in Japanese Patent Provisional Publication No. 11-28994 (on pages 2 to 6 and in FIGS. 1 to 17).
With such a disclosed technology, a load sensor or displacement sensor are mounted to an inside of a bumper of the vehicle to provide output signals and a vehicle speed sensor is mounted to the vehicle to provide a vehicle speed signal. Depending on signal waveforms outputted from the load sensor or the displacement sensor, mounted inside the front bumper, and a signal waveform outputted from the vehicle speed sensor, discrimination is made to find whether the vehicle collides with the pedestrian or a stationary object utilizing a concept in that if a detecting object is a pedestrian, the signal waveform of the load sensor, generated when the pedestrian collides with the vehicle, is restored to its original state at faster time than that generated when the vehicle collides with the stationary object, such as the other vehicle, a wall, a standing timber and a utility pole (hereinafter merely referred to as the stationary object) as disclosed in the above Patent Literature on paragraphs 0027 to 0032.
Such a related art technology is based on a concept in that the signal waveform of the load sensor or the displacement sensor, generated when the pedestrian collides with the vehicle, is continuously generated for a time period shorter than that of a signal waveform generated when the vehicle collides with the stationary object and has an output level lower than that of the signal waveform associated with the stationary object. Depending on such a concept, the signal waveform is arranged to have a given range in a time period for which the sensor output is continuously generated and another given range in an output level of the sensor output to allow discrimination to be made, when the sensor output delivered from the load sensor falls in the given ranges, that the pedestrian collides with the vehicle.
Therefore, in cases where the signal waveform of the sensor output is out of such a given range, an issue arises wherein even in the occurrence of the collision between the pedestrian and the vehicle, the pedestrian detection device erroneously detects that such a collision is associated with the stationary object with the resultant difficulty in correctly detecting the collision associated with the pedestrian. Also, under circumstances where the signal waveform of the load sensor lies in such a given range, another issue comes out wherein if the stationary object has a characteristic closely related to the pedestrian in terms of a mass and rigidity, the pedestrian detection device erroneously detects the collision associated with the pedestrian even in the absence of the collision associated with the pedestrian.